Mirna (Italian: Fiume Quieto , Latin: Ningus Flume ) is a river in Croatia. It rises near the town of Hum in Istria, and flows into the Adriatic Sea near Novigrad. The length of the Mirna river is 53 km, and the towns of Buzet and Motovun lie on it. It got its name from its slow flow.
The riparian ecosystems along the Mirna are characterized by the presence of honeysuckle, white ash and black truffle. The natural landmark of the river is the Motovun forest.
